Vogue dresses Marissa Mayer in an empress’s clothes, but is she really wearing any?

Yahoo’s Marissa Mayer is the CEO du jour. The latest example of her popularity is a spread in the flagship September issue of Vogue, which features a picture of her wearing a blue, sleeveless dress, lying tastefully (if a little uncomfortably-looking) on a white lounge chair, with her blonde hair splayed out like a waterfall and a tablet in her hand. Vogue follows up with a complete week’s worth of outfits chosen for Mayer, from a $4,900 Balenciaga dress to a $4,350 Tiffany watch.

There is no doubt that Mayer has made Yahoo somewhat cool again, partly by buying a bunch of hip startups (most of which you won’t have heard of), and her hiring came after several tumultuous years at the company.

But does Mayer really deserve such attention? The underlying business that makes money for Yahoo, display advertising and search revenue, is still troubled. And the more than 37% rise in Yahoo’s stock price this year stems mostly from the anticipated windfall Yahoo will receive because of its stake in Chinese e-commerce firm Alibaba Group, which is slated to go public.

Alibaba’s reported revenue grew by 71% in the second quarter, while Yahoo reported a 7% sales drop in that same period. Yahoo’s display advertising revenue took a 12% hit while ad sales from search fell by 9%. Some analysts even speculate that without the Alibaba stake, Yahoo could be worth nothing, or even have a negative value.

Of course, she has just been on the job for a year, so she may deserve more time. Yahoo’s acquisitions under her stewardship have been a grab bag with no obvious business rationale (other than Tumblr, which brought Yahoo a bunch of new users), but they have allowed the company to acquire talent, something it was finding very hard to do under Mayer’s predecessors. The hope is that after a while, this talent will start producing great things and that will show in Yahoo’s performance. Those who know Mayer or work with her gush about how smart and impressive she is. Certainly, considering the previous run of CEOs, she’s Yahoo’s best hope so far for getting back on its feet.

But the glowing reviews are a bit premature. Until she starts making a dent in Yahoo’s ad revenue, the company is still struggling and competitors, like Facebook, are surging. And once Alibaba goes public, Yahoo won’t have a crutch for its share price. Then investors will have a clearer picture of the what the empress is really wearing.